In general, examples of a combustor that can heat heating water flowing through the inside of a heat exchanging pipe in a combustion chamber by using a burner may include a boiler and a water heater. That is, the boiler that is used in a general home, a public building, or the like is used for heating and hot water and the water heater heats cold water up to a predetermined temperature within a short time to allow a user to conveniently use the hot water. Most of the combustors such as the boiler and the water heater are constituted by a system that uses oil or gas as fuel and combusts the oil or gas by means of a burner, heat water by using combustion heat generated in the course of the combustion, and supplies the heated water (hot water) to a user.
The combustor is equipped with a heat exchanger for transmitting the combustion heat generated from the burner to the heating water flowing through the heat exchanging pipe.
FIG. 1 is a schematic cross-sectional view of a heat exchanger in the related art.
The heat exchanger includes a heat exchanging pipe 1, fixing plates 2 and 3, flow channel caps 4 and 5, a heating water inlet 6, and a heating water outlet 7.
The heat exchanging pipe 1 has a cylindrical cross-section with ends open and a plurality of heat exchanging pipes 1 is longitudinally stacked. The fixing plates 2 and 3 have pipe insertion holes longitudinally arranged at regular intervals and both ends of the heat exchanging pipes are inserted in the pipe insertion holes, respectively. The flow channel caps 4 and 5 are welded to the fixing plate 2 and 3, respectively, and form parallel flow channels by closing both open ends of the heat exchanging pipes 11. The lower portions of the flow channel caps 4 and 5 are connected with the heating water inlet 6 and the upper portion is connected with the heating water outlet 7.
The fixing plates 2 and 3 and the flow channel caps 4 and 5 are bonded usually by brazing, i.e., braze-welding. Brazing is one type of welding that brings two base metals to weld at a high temperature of 500° C. or more in close contact with each other and welds the base metals by supplying a brazing filler metal therebetween. The brazing is widely used because of the advantages of high bonding strength, precise bonding, and ease of automation. When the two base metals are not in sufficiently close contact with each other in brazing, the base metals are not bonded, and even if they are bonded, the bonding is incomplete. Therefore, it is the most important to bring the two base metals to weld in close contact with each other in brazing.
FIG. 2 is a view illustrating a method of bring the fixing plate 2 and the flow channel cap 4 in sufficiently close contact with each other before brazing in the related art.
The flow channel cap 4 is placed on the fixing plate 2 and then the fixing plate 2 and the flow channel cap 4 are brought in sufficiently close contact with each other by spot-welding at predetermined positions in advance along the joint. Thereafter, brazing is performed in a brazing furnace.
However, this method has a problem in that labor and manufacturing cost increase due to an additional process because spot-welding is necessary before brazing.